My idea is a rugged portable battery with a built in hard drive that can hold a few thousand photos or a few full hd videos (around 128/256gb as a starting point). Possibly solar charging with a high capacity battery of 4 or 5 charges for a modern phone, with a built in high powered torch and more.
This would be useful at festivals/parties for backing up in case of loss or damage to a phone or camera, and/or not having sufficient data or signal to back up to the cloud. This could also be useful for explorers, hikers and extreme sports people having the security of knowing they have a back up of their precious memories.
Water/beer resistance would be something I would look at for in a festival battery so a high IP rating would be something to look at. Temperature may be another factor for the more adventurous users, hiking up mountains etc.
Also having an app that once clicked would export copies of all photos/videos captured in the past 24hrs to the drive would be useful too. Wireless energy and transfer is the way technology seems to be going so maybe while wirelessly charging, data backup could be automatic if the transfer app is open.
I would suggest sticking a speaker on it but adding to the previous ideas already stated could make it too heavy and unwieldy, especially when considering its primary uses and that the speaker would drain the battery making it less useful as a charger.
Basically I would be looking for the Swiss Army Knife for outdoors technology, compact enough to stick in you pocket, flexible enough to have multiple uses, hardy enough to take most things thrown at it.
I hope this idea may be useful although I would not be surprised if someone had suggested something similar a few years ago.
Thank you for taking your time to read this,